Repeater



June 5,Y 1912.8.v

P. J. WALSH REPEATER Filed Feb. 23, 1926. A

xN-vENTo Phi/,.0 Wa/5/7 BY Y /W YITTORNEY M f%|ll\I 50, whic Patented June 5, 1928.

si UNITED STATES PATENT OFFICE.

PHILIP JOHN WALSH, OF SAN FRANCISCO, CAIUORNIA.

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Application lcd February 33, 1926. Serial Io. 89374.

This invention relates to a device for relaying signals, such as Atelephone or telegraph signals. p

When messages are sent overa wire for long distances, the signals become unavoidably attenuated, due primarily to impedance losses and leakage losses. For that reason, it has'been customary to supply relays or repeaters in series in the line, to am- I 1o plify the signaling impulses. Such repeatvers are required to Work in either direction; so that, weak impulses coming from either end of the line are amplified and relayed to the other end. In prior schemes, such relaying Vor re eating lis accomplished only with the aid'o delicate and expensive apparatus, for the amplification must be accom lished without distortion; this is especial y important in telephone work. Furthermore, with many such repeaters, it is diiicult to linstallthem in existmg lines.

It is one of thew ob]ects of my invention to overcome-all these disadvantages, and to provide a simple and eiiicien't repeater that operates without distortion.

It isstill another object of4 my invention to make itpossible to amplify the signaling impulses in such manner that the identity `ot the impulses are never lost; but, instead,

3o an augmentation or building up process is utilized forssuperimposlng upon the weakl signal, impulses that are exactly in phase with those to be amplified.

to make it possible to amplify t e original impulses greatly, so that fewer repeaters need Vbe used in a given length of line. In thisvconnection, my inventlon operates to pick up signals that are very weak, and this too helps to`reduce the number of required repeaters.

My invention possesses many other ad- Vantages, and has other objects whichmay be made more easily apparent from a consideration of one embodiment' of my invention. For this purpose I have shown a form lin the drawings accompanyingand forming part of the present specification. I shall now proceed to describe this form in detail, illustrates the general rinciples of myinvention; but it is to be Aunderstood that this detailed description isnot to be taken ina limiting sense since the scope of my invlention Vis best defined by the appended c alms.

-as of Iinde It is still another object of my! invention' Referrinvr to thedrawings:

The single figure is a wiring diagram of one form of my invention shown installed in a line, such as a telephone circuit.

In this li e, the lines 1 and 2 are shown 'te length, connecting the two subscribers stations 3 and 4. The repeater arrangement can be installed in a short section of the line-about two feet or thereabouts-and acts to augment a weak signal flowing from either direction by inducing, as in a coil 23 in series in the line 1, electrical energy lin phase with the impulses to be amplified. The coil 6 in line 2 is used merely to render the entire arrangement symmetrical.

In order to pass ener at the right phase to coil 23, use 1s made o anl amplifier system that is operated in accordance with the signaling impulses. As one form of such an amplifier system, there islshown a scheme heretofore described and claimed in an ap- Elication filed Feb. 24, 1925 in my name,

aving Serial N o. 11,371, and entitled, Amplifier system. This includes la thermionic amplifier device 7, having a double set of electrodes, therefore being-the equivalent of a pair of single devices, which could in fact be substituted for that shown. The amplilier has a filament 8, heated by the passage of a regulated amount of current from a source 9, such as a battery. On either side of the filament 8 there is a late 10 or 1.1, to which the electrons given o from the {ilament 8 are attracted.

The currents flowing between lates l1 and 10 to the filament 8 are fur ed from a common source 12, which is .so arranged ,this resistance, coil 17, plate 11, to filament 8; and the other part goes through the right hand portion of resistance 16, coil 18, plate 10,to filament 8, where the currents recom- 105 bine, and flow through coil 14 to the nega-.

tive side of battery 12.

The coils 17 and 18 are differentially arran d on a leg 19.0f a core 20, and the tap 15 1s adjusted to such a Yposition that the 110 t ereof in a well-understoodmanner.

v coils exactly neutralize each other while no impulses pass between the stations. Control s ace current paths to vary the impedances These nelectrodes are controlled in accordance with the impulses in lines 1 and 2, to produce a large unbalance of magnetism in core 20, .and thereby to induce a current in the coil I" 23 that is placed on core 20. Let us assume for example that there is imparted to electrode 21 a negative potential with respect' to filament 8; then the space current between this filament and plate 10 is reduced. Since l5 in this instance constant current is supplied to both space current paths, this reduction causes a corresponding increase of current in the coil 17; The coils 17 and 18 being opposed, this means an increasing iiux in one direction through coil 23, setting up an E. M. F. therein which is useful in augmenting the current How to amplify the signal passing therethrough, in a manner to be hereinafter described.

The reverse effect takes place when electrode 21 is charged positive; that is, the E. M. F. induced in coil 23 increases in the o posite direction than before; but due to t e arrangement that will be described, this direction changes only when the direction of the signal impulse changes, whereby the coil 23 nevertheless augments these impulses.

The unbalance between coils 17 and 18 can easily be accentuated by the aid of the control electrode 22, which is caused to vary' the im edance of the 'space current path between lament 8. and late 11, in a sense o posite to that of the ot er space current patlh. a For this purpose, another coil 24 is induc- 4ov tively associated with coils 17 nand 18 so as to respond also to the unbalanced condition, andis connected between the filament 8 and electrode 22, .in such manner as to influence the space current in the desired direction.

To control the building up process of the magnetism in core 20, an adjustable armature 25 is inserted in a gap between the coils 18 and 24.-

The initiation of-the actions in tube. 7 is controlled by grid 21, the circuit for which 155i which coil 5 paralleling coil 23, is the primary, to grid 21. It is evident that the combined potentials of coils 26` and 29 are used to influence grid 21, and the arrangement Vis such that th1s combined potential 1s always o0 the exact equivalent of the impulse being transmitted. For this pur ose, coils 5, 23, and 29 are so proportione that the E. M. F. across coil 29 is exactly the same as that across coil 23. Also, coils 23 and 5 are made 65 with the same number of turns 'and of ex-I actly the same im edance'. vCoils 2.9 andj26 are in bucking re ation as regards their E. 'electrodes 21.and 22 are interposed in the M F the vbattery 12 merely supplies equal and o posite currents to coils 17 and 18, since t e control 4electrodes 21 and 2 2 are inactive, and the space current paths accordingly having equal impedances. Now let us assume that an impulse begins, say in a direction indicated by arrow 30, and is originatedv at station v3. At first, 4the current divides at point 31, half going through coil 23, and the other half through lcoil 5. It recombines, and flows through primary 28, to subscriber #2.

An E. M. F. is induced in coil 29 of' such direction as will make, let us sa the right hand terminal positive,and an M. F. is also induced Iin coil 26 that will make its right hand. terminal negative. The E. M. .F.s at this instant in coils 29 and 26 are cumulative, and serve to impress a positive potential difference between filament 8 and grid 21. This causes an instant increase in current through coil 18, and a corresponding decrease through coil 17; the coil 24acts to reinforce this dlference.- A magnetic field is thus being set u in core 20 through" the legsl thereby induced in it in a direction repre-- f sented b arrows 30. It is evident that this E. M. serves to send a current through v coil 23 that assists the current from station 3, vand is in a direction opposing the current the E. M. F. in coil 29 is reversed, `and now bucks that of the coil 26. This E. M. F. is an exact measure of the boosting E. M. F. of

coil 23, as specied heretofore; therefore the nisl .resultant E. M. F. which isimpressed between grid 21 and filament 8is exactly equal to that of the original impulse. This'can be readily appreciated from the fact that coil 26 -responds to the reinforced signal,

while coil 29 responds to the reinforcement, 'and therefore the difference in response is that which would exist if the signal impulso alone were used. In -this way, it is certainv that the building up process produced by the audion arrangement is ke t under proper control and 1s never permltted to cause 1nstability.l Furthermore, variations in 'the' line im edance can have no appreciable effect upon t e operation of this repeating actlon,

since coils 29 and 26 automatically subtract these variations.

An impulse startin in the opposite direction, as indicated by otted arrows 33, causes a reversal in the actions, such that the coil 23 becomes a source of potential which is nevertheless in phase with thisA impulse. Thus the left hand terminal of coil 29 is momentarily positive; and the left hand terminal of coil 26` is negative; grid 21 acquires a negative charge, causing the coil 17 to over ower coil 18, and an increasing magnetic ux exists through coil 23in an opposite direction than before. Therefore the phases are again correct.

It is also readily seen that the coil 23 virtually actsas a boostin E. M. F. in series with the line, and that t is takes lace irrespective of the reversal of the line M. F. Therefore it is immaterial, so far as the repeater is concerned, where the impulse ori inates, whether at subscriber #l or su scriber #2. It can readily be installed in a single line; thecoil 6 acting to insert in the i other line, a balancing impedance, whereby conditions remain balanced.

I claim:

1. In a system 'of the character described, a circuit through which impulses ma be transmitted in'elther direction, an amp iier having an output circuit in series in thev circuit, and means for affecting said amplifier so as to cause it to transmit a boosting electromotive force to the circuit for either direction of transmission, comprjsin means operated in accordance with the diiierencev between the augmented impulse and the eil'ect of the amplifier in the system.

2. In a system of the character described,`

a circuit through which impulses ma be transmitted in either direction, an amplifier having an output ycircuit in series in the circuit, and means for affectingsaid ampliiier so as to cause it to transmit a boosting electromotive force to the circuit, comprising a coil connected in the system in such a manner that an electromotive force exists across it that is an exact measure of the electromotive force of the amplifier output both in direction and amount, and a coil having an electromotive force which is a measure of the augmented impulse, said two coils being connected in opposing series relation.

3. In a system of the character described, a circuit t rough which impulses may be transmitted in either direction, a transformer having a primary coil in series with said circuit, another transformer having its primary in series with said circuit, both of said transformers having secondary coils, the secondary coils being connected in series opposed relation, an amplifier operated in accordance with the combined electromotive force of the said secondary coils, and means whereby the output electromotive force of the amplifier is lmpressed in the circuit in parallel with the primary coil of the first mentioned transformer.

4. The system as claimed in claim 3, in which the secondary coil of the first mentioned transformer has such number of turns that it has an electromotive force across it that is always equal to the electromotive force of the Aampllier output.

' 5. The system as claimed is claimv 3, in which the amplifier comprises means forming a pair of space current paths for electronic emission, and a source of constant direct current for said paths, the combined electromotive force of the two secondary coils actin to vary the-relative impedances of thev pat s, and the variations in said impedances acting to iniuence the output electromotive force.

6. The system vas claimed in claim 3, in which the secondary coil of the first mentioned transformer has such number of turns that it has electromotive force across it that is always equal to the electromotive force of the amplifier output, and in which the amplifier comprises means forming a pair of space current paths for electronic emission, and a source of constant direct current for said paths, the combined electromotive force of the two secondary coils acting to var the my hand.

. PHILIP JOHN WALSH. 

